WMG / Little Sweetheart

That barge does not have good intentions.
Think about it. The barge that saved Elizabeth didn't go to the police or go and get her medical help and they don't seem to be too concerned about her well-being. They didn't save her to help her, they did it to enslave her.

John Hurt and Karen Young are responsible for the lack of anything from the child actresses, and no proof Cassie ever existed under that name.
Look at John Hurt. He has had an insanely long career. Karen Young has also been around for decades. Now then, look at our two child stars. This was the only film for one of them and one of the few for the other. That's not the only thing, though. There are extras who were in this and at best one or two other things, including one who was on The Love Boat, this and nothing else. How is this film killing careers? John Hurt and Karen Young used magic. They drained all the fame the kids, as well as a few others, may have one day earned. The first attempt was on Cassie, the girl who played Thelma. That's why this film seems to be the only thing on the entire internet that can show she ever even existed. John Hurt made the spell too powerful and erased almost every trace of her from the universe. Karen, who has been in less things, was a bit easier on people, so they go a few bit parts and then fell of the face of the Earth. John, on the other hand, continued to drain people dry. Had they been stopped. Cassie would have had decades more fame.

That last scene was forced in by the executives.
It rips too many plot holes in the plot to have been something the generally competent writer would have done. First off, she was face down, at a distance of at least five minutes and in the ocean. Secondly, she had two bullets in her. Thirdly, the ship didn't take her to the police or get her medical care. Fourthly, it just doesn't make sense!

The last scene is a dream.
Think about it, Thelma was, for the first time in a long time, not all alone. She said she had no friends at boarding school and seems to be the only kid in town. It would explain why everyone fails logic forever, from the way biology just doesn't work like that to why the ship didn't go to the cops or hospital.

Elizabeth has amnesia.
While it doesn't help explain why the ship did nothing, or why biology took a vacation, it at least explains why she didn't go to the police.

Elizabeth came back wrong.
Elizabeth actually died. The girl the barge picks up? Now, that's a different story . . .